2. Field of the Invention
The present invention relates to a Minimization of Drive Test (MDT) measurement device and method. More particularly, the present invention relates to a device and method for determining a measurement cycle of a radio channel measurement cycle for collecting radio channel information to be used for optimization of a service area for a terminal operating in standby mode.
2. Description of the Related Art
Typically, mobile communications have been developed for the user to communicate while moving. With the rapid advance of technologies, the mobile communication system has evolved to a level capable of providing a high speed data communication service as well as a voice communication service. Recently, the 3rd Generation Partnership Project (3GPP), as one of the next generation mobile communication standardization organizations, is in the progress of standardization of Long Term Evolution-Advanced (LTE-A). LTE-A is a high speed packet-based communication technology supporting a data rate higher than that of the current mobile communication technology under the objective to complete the standardization in late 2010.
With the evolvement of the 3GPP standard, many discussions are being conducted for optimizing a radio network in addition to the effort for increasing the data rate. In the initial radio network configuration or optimization stage, a base station or a base station controller should collect radio environment information related to its own cell coverage. This process is called Drive Test. The conventional drive test is performed in such a way that an operator carries a test apparatus on a vehicle while performing the measuring task repeatedly for a long time. The measurement result is used to configure the system parameters of the base stations or base station controllers. Such a conventional drive test increases total costs and time for optimizing and maintaining the radio networks.
In order to improve the radio environment analysis and manual configuration process while minimizing the number of times of the drive test, research is being conducted under the title of Minimization of Drive Test (MDT). MDT is characterized in that the terminal transfers the radio channel measurement information to the base station periodically or in response to a specific event. The operation of the terminal transmitting the measured radio channel information and other supplementary information to the base station is referred to as MDT measurement information report hereinafter. The terminal transmits the channel measurement result immediately when it can communicate with the base station or, if the communication with the base station is unavailable, retains the MDT measurement information for transmission when it becomes possible to communicate with the base station afterward. The base station uses the MDT measurement information received from the terminal for optimization of the cell region. In LTE-A, the MDT measurement information reports are classified according to User Equipment (UE) Radio Resource Control (RRC) state as shown in Table 1.
TABLE 1RRC state of UEMDT measurement information report operationIdle modeLogging and deferred reportingConnected modeImmediate reporting
In Table 1, if the UE is in the state of having no communication with an evolved Node B (eNB), this means that the UE is in idle mode. Otherwise, if the UE is in the state of having communication with the eNB, this means that the UE is in connected mode. In case of MDT, since the channel information measured by the UE is transmitted by RRC signaling, the UE in idle mode does not transition to the connected mode for the information transmission. Accordingly, the transmission of the channel measurement information is deferred until the UE transitions to the connected mode. The UE collects the radio channel information at an MDT measurement interval in the connected mode or the idle mode. In order to measure the radio channel in idle mode, the UE has to turn on its receiver, resulting in power consumption. Accordingly, it is preferred to perform the MDT measurement and MDT report efficiently while minimizing the power consumption of the UE.